Medical handpiece with automatic power switching means

ABSTRACT

A medical instrument includes a handpiece, an electromechanical transducer disposed in the handpiece, and an electrical circuit disposed at least partially in the handpiece for supplying alternating electrical current of a predetermined frequency to the transducer. A probe is operatively connected to the transducer for transmitting vibrations generated by the transducer to an operative site in a patient. A switching device is mounted to the handpiece and is operatively connected to the circuit and the transducer for enabling the supply of power to the transducer during a motion of the probe in a preselected direction relative to the handpiece and for disabling the supply of power to the transducer upon a termination of motion of the probe in the preselected direction.

BACKGROUND OF THE INVENTION

This invention relates to a medical instrument and to an associatedmethod. More particularly, this invention relates to a medicalinstrument and method wherein power to an operative tip is automaticallycontrolled.

Ultrasonic devices have been used to remove soft and hard tissue frommammalian bodies for over three decades, at least. These devices andmethods for their use have been well documented in the art, such as U.S.Pat. No. 4,223,676 to Wuchinich, U.S. Pat. No. 4,827,911 to Broadwin andU.S. Pat. No. 5,419,761 to Narayanan et al. Applications includephacoemulsification, ablation of tumors in the liver and spine andsubcutaneous removal of adipose tissue, also known as ultrasonicliposuction.

Most of the instruments used for these applications have severalelements in common. These are an electrical generator which transformsline or battery power to relatively high voltage RF frequencies in the20 kc to 100 kc range, a transducer of either a magnetostrictive orpiezoelectric type and a probe or horn which is generally manufacturedfrom titanium and amplifies the motion of the transducer fromapproximately 20 microns to over 400 microns in some cases. Means havebeen disclosed which allow the surgeon the ability to switch the outputpower on or off on demand. These include footswitch controls, finger orthumb switches on the handpiece or even by voice commands if theelectronic generator includes the prerequisite software and electronics.

All of these means require that the surgeon coordinate the applicationor removal of ultrasonic power to the precise moment at which it isrequired. In spinal or brain surgery, this is not difficult, since theapplication of the power is not continuous and he or she has completeview of the operative site. By simply moving his hand, he is able toapply power to the surgical site and remove the tip of the probe evenwhen the power is on, limiting the power input to tissue. In this way,tissue temperature rise is minimized and collateral damage is curtailed.

However, in applications such as liposuction, the surgeon would have adifficult time in controlling power requirements. In this case, thesurgeon moves the handpiece with a piston like action, alternativelyadvancing and retracting the cannula in a predetermined pattern. SeeU.S. Pat. No. 5,527,273 for a more complete description of this action.Since the sides of the long cannula are in contact with the tissue atall times, power is being applied to the tissue as long as the probe isactivated with ultrasonic energy. In actuality, the power is onlyrequired on the pushing stroke, since the ultrasonic power ablates thetissue in direct contact with the distal end of the probe. As the tissuedisrupts, it liquefies and the cannula can be advance. In this way,channels or tunnels are created in the adipose tissue.

When the probe is pulled back to be repositioned and start anothertunnel, the tissue contacts the side of the probe. Power is still beingapplied but tissue liquefaction does not occur, since it is thecavitation and shearing forces created by the probe tip that liquefiesand emulsifies the cells. Therefore, this energy can be considered wasteand it actually goes into tissue heating. The longer the probe is used,the higher the temperature rise will be. If the temperature rises abovethe necrosis point, burning, scarring and other deleterious effects willarise.

It would be difficult and tiring for the surgeon to time the on and offcontrols with his hand movements, since they are rapid and repetitive.It would be more desirable to have an automatic means to determine thepower requirement and have the machine apply energy only when mostneeded.

Several embodiments for reducing the amount of ultrasonic powerdelivered to the tissue or samples have been known to the art for manyyears. One old technique is pulsing of the output. By automaticallyturning the output power on and off at specific duty cycles, the powermay be reduced in inverse proportion to the output duty cycle. Forinstance, if the output power was turned on for 2/10ths of a second andshut off for the remainder of that second, it would be said the outputpower had a 20% duty cycle. At the beginning of the next second, thepower is turned back on for 2/10ths of a second and so forth. The powerinput to the tissue or sample would be reduced by 80% over a givenperiod. However, this embodiment does not turn off the power completelywhen not needed, i.e. on the return stroke, it only lessens it. In fact,the power is even reduced on the push stroke, when it is most neededincreasing the effort needed to advance the cannula through the body.

OBJECTS OF THE INVENTION

An object of the present invention is to provide a medical instrumentand/or an associated method wherein the control of power transmission toan operative tip is facilitated.

Another object of the present invention is to provide such a medicalinstrument and/or an associated method wherein power transmission to theoperative tip is effectuated automatically, without requiring anydedicated separate action on the part of the surgeon.

A related object of the present invention is to provide a liposuctioninstrument and/or an associated surgical method for reducing, if notminimizing, trauma to tissues of a patient.

Yet another object of the present invention is to provide an ultrasonicliposuction instrument that is easier to use than conventionalultrasonic liposuction probes.

These and other objects of the present invention will be apparent fromthe drawings and descriptions herein. Although every object of theinvention is attained by at least one embodiment of the invention, thereis not necessarily any embodiment in which all of the objects are met.

SUMMARY OF THE INVENTION

The present invention is directed in part to a medical instrument and anassociated method wherein power is automatically delivered to anoperative tip only when the instrument is being advanced through tissuesof a patient. Energy or power is automatically turned off when theinstrument and particularly the operative tip is no longer beingadvanced, for instance, is being retracted.

A medical instrument in accordance with the present invention comprisesa handpiece, an electromechanical transducer disposed in the handpiece,an electrical circuit disposed at least partially in the handpiece forsupplying alternating electrical current of a predetermined frequency tothe transducer, a probe operatively connected to the transducer fortransmitting vibrations generated by the transducer to an operative sitein a patient, and a switching device mounted to the handpiece andoperatively connected to the circuit and the transducer for enabling thesupply of power to the transducer during a motion of the probe in apreselected direction relative to the handpiece and for disabling thesupply of power to the transducer upon a termination of motion of theprobe in the preselected direction.

The handpiece may include a main body portion and a grip portion movablycoupled to one another. In that case, the switching device including twoelectrical contacts respectively mounted to the main body portion andthe grip portion, the switching device further including a springcarried by the handpiece for biasing the main body portion and the gripportion relative to one another.

Typically, the spring is a compression spring disposed between the bodyportion and the grip portion of the handpiece for biasing them away fromone another to thereby maintain the electrical contacts spaced from oneanother. In this embodiment, the handpiece has a distal end and aproximal end, the probe extending from the distal end of the handpiece,while the preselected direction is a distal or forward direction. Thegrip portion is located proximally of the main body portion. Upon amanual pushing of the handpiece via the grip portion, the frictionalcontact of the probe with the tissues of the patient reduces the forwardmotion of the body portion relative to the motion of the grip portion,so that the electrical contacts engage and enable a current flow to thetransducer.

In a particularly useful embodiment of the invention, the probe iselongate, the predetermined frequency is an ultrasonic frequency, andthe instrument is an ultrasonic liposuction instrument.

In accordance with an alternative feature of the invention, theswitching device is an inertial mass switch or a load sensor.

Another embodiment of a medical instrument in accordance with thepresent invention comprises a handpiece, an operative tip connected tothe handpiece, and transmission means mounted at least in part to thehandpiece and operatively coupled to the operative tip for supplyingpower to the operative tip, whereby the operative tip is enabled toeffectuate a predetermined kind of surgical operation on a patient. Thisembodiment additionally comprises a motion sensor mounted to thehandpiece and operatively connected to the transmission means forenabling the transmission means to supply power to the operative tiponly during motion of the operative tip in a preselected directiondefined relative to the handpiece.

The motion sensor may be a spring-loaded switch. Where the handpieceincludes a main body portion and a grip portion movably coupled to oneanother, the switch includes two electrical contacts respectivelymounted to the main body portion and the grip portion and furtherincludes a spring carried by the handpiece for biasing the main bodyportion and the grip portion relative to one another.

Alternatively, the motion sensor may be an inertial-mass-type sensor ora load sensor.

A method for performing a surgical operation utilizes, in accordancewith the present invention, a medical instrument having a handgrip at aproximal end and an operative tip at a distal or free end. The methodcomprises (1) moving the medical instrument in a preselected directionrelative to the medical instrument, (2) by virtue of the moving of themedical instrument in the preselected direction, automaticallytransmitting power to the operative tip during the moving of the medicalinstrument in the preselected direction, (3) terminating the motion ofthe medical instrument in the preselected direction, and (4) by virtueof the terminating of the motion of the medical instrument,automatically terminating the transmission of power to the operativetip.

The medical instrument may be provided with a motion sensor. In thatevent, the automatic transmitting of power to the operative tip includesoperating the sensor to detect motion of the medical instrument in thepreselected direction, whereas the automatic terminating of the powertransmission to the operative tip includes operating the sensor todetect a cessation of motion in the preselected direction.

Pursuant to another feature of the present invention, the method furthercomprises transmitting power to the operative tip only when the medicalinstrument is being moved in the preselected direction. Morespecifically, the method comprises transmitting power to the operativetip only when the medical instrument is being moved in the preselecteddirection through a mass providing frictional resistance to passage ofthe instrument.

In a medical instrument in accordance with the present invention, thecontrol of power transmission to an operative tip is facilitated bybeing made dependent on the motion of the instrument through the organictissues of the patient. The turning of power alternately on and off isachieved automatically without the surgeon having to operate anycontrol. The surgeon merely moves the instrument in the desireddirection and back again.

A medical instrument in accordance with the present invention reducestrauma to tissues of a patient, for example, in ultrasonically assistedliposuction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial longitudinal cross-section view of a handpiece foran ultrasonic liposuction instrument, showing a spring-loaded handgripcontaining a motion-actuated power control switch, in accordance withthe present invention.

FIG. 2 is a partial longitudinal cross-section view of anotherembodiment of a handpiece for an ultrasonic liposuction instrument,showing another spring-loaded handgrip containing a motion-actuatedpower control switch, in accordance with the present invention.

FIG. 3 is an end elevational view of the handpiece of FIG. 2.

FIG. 4 is a partial longitudinal cross-sectional view of a furtherembodiment of a handpiece for an ultrasonic liposuction instrument,showing an inertial type motion-responsive power control switch, inaccordance with the present invention.

FIG. 5 is partially a block diagram and partially a schematic partialcross-sectional view of yet another handpiece for an ultrasonicliposuction instrument, showing a load-type motionsensitive powercontrol switch, in accordance with the present invention.

DEFINITIONS

The term “medical instrument” is used herein to denote any device thatis used in contact with organic tissues of a patient to perform adiagnostic or therapeutic procedure.

The term “operative tip” as used herein designates a portion of amedical instrument that is placed into contact with organic tissues of apatient during a medical procedure. Typically, the operative tip isfunctional to effect a surgical operation on organic tissues. Forinstance, an operative tip may be a free end of an ultrasonicallyvibrating probe or cannula. Alternatively, an operative tip may be acauterization element of an electrocautery applicator, a scissors, avibrating scalpel, a suction port, an irrigation port, etc.

The word “handpiece” as used herein relates to a casing, frame, holder,or support which can be manually carried and manipulated during amedical operation on a patient.

A “power-transmission circuit” or “circuit” as that term is used hereinmeans any hardware used to move energy from a source to a load. Thepower transmitted may be mechanical, electrical, magnetic, hydraulic, orpneumatic. The hardware may include mechanical structural elements,transducers, electrical circuits, electrical leads, magnetic materials,and hydraulic or pneumatic conduits and valves. The hardware mayadditionally include power sources: voltage or current sources, magnets,pressurized or pressurizable reservoirs of fluid of air.

The term “switching device” is used herein to generally describe anymanually operable control utilizable in conjunction with apower-transmission circuit for alternately enabling and disabling theflow of power through the circuit. A switch may be mechanical,electrical, electromagnetic, magnetic, hydraulic, or pneumatic. Specificexamples include spring-loaded electrical contact switches, gravity orinertial switches, and load switches.

A “motion sensor” as that term is used herein refers to any detectordevice responsive to a velocity or acceleration. A motion sensor may bemechanical or electromechanical as in the case of a micro-switchfunctioning in the manner of a hair sensor. A motion sensor may take theform of a gravity switch or an inertial switch or a mercury switch. Amotion sensor may be a load sensor such as a stack of piezoelectriccrystals sensing compression due to a resistance to motion.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Together with improvements disclosed herein, the drawings show sectionsof a medial instrument handpiece disclosed in U.S. Pat. No. 5,769,211,the disclosure of which is hereby incorporated by reference.

As illustrated in FIG. 1, an ultrasonic handpiece comprises a handgripportion in the form of a sleeve 12 that surrounds and is movably mountedto a transducer array 14. Transducer array 14 includes a front driver 16and a stack of piezoelectric crystals 18. Front driver 16 is coupled toan ultrasonic horn 20 that amplifies ultrasonic pressure waves producedby the stack of crystals 18. Front driver 16 is provided at a vibrationnode with an outwardly extending circumferential flange 22, while sleeve12 is provided with an inwardly extending circumferential flange (or aplurality of angularly spaced inwardly extending projections) 24. Ahelical compression spring 26 surrounds front driver 16 and issandwiched between flanges 22 and 24. Compression spring 26 biasesflanges 22 and 24 away from one another.

Flange 24 carries a switch 28 that is connected to an electrical a-cpower supply 30 via a pair of leads 32. Switch 28 controls thetransmission of an ultrasonic-frequency electrical waveform from supply30 to transducer array 14. Switch 28 includes a switch body 36 providedwith an actuator 38 such as a telescoping plunger element. Switchactuator 38 is attached directly to flange 22 and or indirectly toflange 24 via switch body 36.

As disclosed more fully hereinbelow with reference to FIGS. 2 and 3,sleeve or handgrip 12 is shiftably mounted to a casing or housing (notshown in FIG. 1) and has a length determined from ergonomic studies ofthe average width of surgeons' hands. The spring 26 provides enoughforce to maintain actuator 38 extended from switch body 36 so thatinternal switch contacts (not shown) are separated when the instrumentis at rest. A surgeon grasps the handpiece around the sleeve 12 andprovides force by pushing the cannula or probe 39 into the targettissues of the patient. Spring 26 is compressed by that force so thatthe electrical internal contacts of switch 28 close, transmittingelectrical power to transducer array 14 as previously disclosed. As longas sufficient resistance exists against the forward movement of thehandpiece and cannula 39, the switch will remain closed and the outputenergy will be on.

As the surgeon begins to extract the instrument from the patient, theforce on the distal end of the cannula or probe 39 is relieved. Spring26 pushes the actuator 38 out of switch body 36 thereby separating theinternal switch contacts turning the power off. As the surgeon continuesto retract the handpiece, the switch 28 remains open, therebyeliminating power input to the site for the entire time the cannula 39is moving backwards. Tissue temperature cannot rise during theretraction phase and in fact lowers since energy input during ultrasoundactivation is allowed to conduct away. If the spring 26 has asufficiently great spring constant, the switch contacts will remainapart even if the handpiece is at rest. Therefore, if the surgeon stopsto rest or otherwise pauses the stroking action, the ultrasonic powerwill remain off until he repositions and advances the cannula 39 again.

FIGS. 2 and 3 show a handpiece like that of FIGS. 2A and 2B of U.S. Pat.No. 5,769,211 modified to provide an actuator sleeve 40 which surroundsa substantially cylindrical handle or handpiece case 42. Actuator sleeve40 has an internal surface provided with a plurality of angularlyequispaced grooves 44 which define a plurality of angularly equispacedribs 46. Ribs 44 have an internal diameter which is slightly greaterthan the outside diameter of handpiece case 42 upon which the ribs ride.In this manner, a sliding fit is achieved which allows sleeve 40 to betranslated alternately in a distal direction 48 and a proximal direction50. A shoulder, ledge or abutment 52 on sleeve 40 is engageable with ashoulder 54 of case 42 to prevent sleeve 40 from being slid off the backof the case. Recesses or grooves 46 on the inner diameter of sleeve 40reduce the amount of material in contact with handpiece case 42. Thisreduced contact decreases friction and prevents debris from collectingbetween sleeve 40 and handpiece case 42, which prevents the sleeve fromsticking or binding.

Sleeve 40 has a distally directed surface (not designated) which isfaced with an electrically conductive lining 56 which does not corrodein the presence of steam or detergents, such as stainless steel. Thislining 56 is either glued or staked to sleeve 40, using methods known tothe art. A mating face 58 is fashioned on handpiece case 42. This face58 is manufactured from a material which is generally nonconductive,such as thermoplastics. A switch 60 has parts (see U.S. Pat. No.5,769,211) provided along lining 56 and face 58, those parts closing theswitch upon an approach of lining 56 and face 58. The closing of switch60 conducts current from a power supply 62 to a transducer array orpiezoelectric crystal stack 64.

Low friction bushings 66 and 68 or other such bearings are located onthe handpiece body or case 42 and locate the sleeve so that it isessentially coaxial with the handpiece body itself.

In order to allow an automatic opening of switch 60 upon an interruptionin forward motion of the instrument, owing to the surgeon's reduction inforward force on sleeve 40, sleeve 40 is spring loaded. As depicted inFIG. 2, two helical or coil springs 70 and 72 are placed between sleeve40 and handpiece face 58. Coil springs 70 and 72 are spaced 90° fromeach contacts of switch 60 (see U.S. Pat. No. 5,769,211). Two pins 74and 76 are pressed into handpiece face 58 and are thereby fixed inplace. Pins 74 and 76 engage blind holes 78 and 80 drilled into sleeve40, whereby the pins perform both a locating or mounting function forcoil springs 70 and 72 and a keying junction for sleeve 40 to preventthe sleeve from rotating about a longitudinal axis 82 of handpiece case42.

The coil springs 70 and 72 provide sufficient force to keep the contactsof switch 60 separated during rest. As the surgeon grasps the handpiecearound the sleeve 40, he of she exerts a force in the distal direction,thereby pushing the cannula or probe 83 into the target tissues. Springs70 and 72 are compressed by the applied force and the contacts of switch60 close, turning the energy on as previously disclosed. As long assufficient resistance exists against the forward movement of thehandpiece and cannula 83, the switch 60 will remain closed and theoutput energy will be on.

As the surgeon begins to retract the instrument, the force on the distalend of the cannula or probe 83 is relieved. The springs 70 and 72 pushthe switch contacts apart and the output power is turned off. As thesurgeon continues to retract the handpiece, the switch 60 remains open,thereby eliminating power input to the site for the entire time thecannula 83 is moving backwards. Tissue temperature cannot rise duringthe retraction phase and in fact lowers since energy input duringultrasound activation is allowed to conduct away. If the springs 70 and72 have sufficient energy, the switch contacts will remain apart even ifthe handpiece is at rest. Therefore, if the surgeon stops to rest orotherwise pauses the stroking action, the ultrasonic power will remainoff until he repositions and advances the cannula 83 again.

Another embodiment, illustrated in FIG. 4, incorporates an inertial masstype switch. Here a relatively large mass 84 is suspended by a lowfriction bearing (not shown) inside a casing or housing 86 so that themass can move parallel to a long axis 88 of the handpiece. As thehandpiece is moved back and forth rapidly, the inertial mass 84 moves inthe opposite direction as per Newton's laws of motion. As the mass 84engages switch contacts 90 and 92 at either end of its travel path, theoutput of the ultrasound device may be turned on and off simultaneously.Preferably, the switching action occurs upon an initial engagement ofthe mass 84 with contacts 90 and 92. Light springs (not shown) can beused to center the mass 84 when at rest. The benefit of this is that thesurgeon does not have to overcome force of a heavier spring to activatethe output power. It is also useful when the resistance of the tissue orother load is slight.

In another embodiment, depicted diagrammatically in FIG. 5, a tubularhandpiece casing 94 is connected to or incorporates a load-sensingdevice 96. This device could be a piezoelectric sensor, a strain gaugeor other force or load-sensing element known to the art. Here, the levelof force is measured. An electric switching circuit 98 incorporateslogic or sensing circuits 100 that both measure the magnitude this forceand provide an analog or digital signal 102 proportional to it. Theoutput amplitude or energy from an ultrasonic transducer array 104 maybe modulated by this signal, via a modulator 106 and a modulated powersupply 108, to provide either a stepped on/off output or an output powerlevel that is directly or inversely proportional to the applied force.FIG. 5 shows a simplified or schematic form of this embodiment. Theelectronic interface circuits required for this type of control are wellknown to the art.

Although the invention has been described in terms of particularembodiments and applications, one of ordinary skill in the art, in lightof this teaching, can generate additional embodiments and modificationswithout departing from the spirit of or exceeding the scope of theclaimed invention. For example, although the described surgical methoddescribes a liposuction procedure done during plastic surgery, manyother surgical procedures may benefit from this invention. Accordingly,it is to be understood that the drawings and descriptions herein areproffered by way of example to facilitate comprehension of the inventionand should not be construed to limit the scope thereof.

1. A medical instrument comprising: a handpiece; an electromechanicaltransducer disposed in said handpiece; an electrical circuit disposed atleast partially in said handpiece for supplying alternating electricalcurrent of a predetermined frequency to said transducer; a probeoperatively connected to said transducer for transmitting vibrationsgenerated by said transducer to an operative site in a patient; and anat least partially automatic switching device mounted to said handpieceand operatively connected to said circuit and said transducer enablingthe supply of power to said transducer during a motion of said probe ina preselected direction defined relative to said handpiece andautomatically disabling the supply of power to said transducer upon atermination of motion of said probe in said preselected direction sothat power is supplied to said transducer only when said probe is movingin said preselected direction.
 2. The instrument defined in claim 1wherein said handpiece includes a main body portion and a grip portionmovably coupled to one another, said grip portion being sufficientlylarge to accommodate an entire adult hand, said switching deviceincluding two electrical contacts respectively mounted to said main bodyportion and said grip portion, said switching device further including aspring carried by said handpiece for biasing said main body portion andsaid grip portion relative to one another.
 3. The instrument defined inclaim 2 wherein said handpiece has a distal end and a proximal end, saidprobe extending from said distal end of said handpiece, said preselecteddirection being a distal or forward direction, said grip portion beinglocated proximally of said main body portion, said spring being acompression spring disposed between said main body portion and said gripportion.
 4. The instrument defined in claim 3 wherein said probe iselongate, said predetermined frequency is an ultrasonic frequency, andthe instrument is an ultrasonic liposuction instrument.
 5. Theinstrument defined in claim 2 wherein said grip portion is a sleevesurrounding said main body portion, said sleeve having a length parallelto an axis of said main body portion approximately equal to an averagewidth of surgeons' hands.
 6. The instrument defined in claim 1 whereinsaid handpiece has a distal end and a proximal end, said probe extendingfrom said distal end of said handpiece, said preselected direction beinga distal or forward direction.
 7. The instrument defined in claim 1wherein said predetermined frequency is an ultrasonic frequency and theinstrument is an ultrasonic medical instrument.
 8. The instrumentdefined in claim 1 wherein said switching device includes means fordisabling the supply of power to said transducer solely in response totermination of motion of said probe in said preselected direction.
 9. Amedical instrument comprising: a handpiece; an electromechanicaltransducer disposed in said handpiece; an electrical circuit disposed atleast partially in said handpiece for supplying alternating electricalcurrent of a predetermined frequency to said transducer; a probeoperatively connected to said transducer for transmitting vibrationsgenerated by said transducer to an operative site in a patient; and anat least partially automatic switching device mounted to said handpieceand operatively connected to said circuit and said transducer forenabling the supply of power to said transducer during a motion of saidprobe in a preselected direction defined relative to said handpiece andfor automatically disabling the supply of power to said transducer upona termination of motion of said probe in said preselected direction,wherein said switching device is an inertial mass switch.
 10. Theinstrument defined in claim 9 wherein said inertial mass switch includesa mass suspended in said main body portion so that said mass can movealong a travel path parallel to an axis of said main body portion andrelative to said main body portion.
 11. The instrument defined in claim9 wherein said switching device further includes means operativelyconnected to a load sensor for modulating an output of said electricalcircuit in accordance with a level of force detected by said loadsensor.
 12. A medical instrument comprising: a handpiece; anelectromechanical transducer disposed in said handpiece; an electricalcircuit disposed at least partially in said handpiece for supplyingalternating electrical current of a predetermined frequency to saidtransducer; a probe operatively connected to said transducer fortransmitting vibrations generated by said transducer to an operativesite in a patient; and an at least partially automatic switching devicemounted to said handpiece and operatively connected to said circuit andsaid transducer enabling the supply of power to said transducer during amotion of said probe in a preselected direction defined relative to saidhandpiece and automatically disabling the supply of power to saidtransducer upon a termination of motion of said probe in saidpreselected direction so that power is supplied to said transducer onlywhen said probe is moving in said preselected direction, wherein saidswitching device includes an electromechanical load sensor.
 13. Amedical instrument comprising: a handpiece; an electromechanicaltransducer disposed in said handpiece; an electrical circuit disposed atleast partially in said handpiece for supplying alternating electricalcurrent of a predetermined frequency to said transducer; a probeoperatively connected to said transducer for transmitting vibrationsgenerated by said transducer to an operative site in a patient; and anat least partially automatic switching device mounted to said handpieceand operatively connected to said circuit and said transducer forenabling the supply of power to said transducer during a motion of saidprobe in a preselected direction defined relative to said handpiece andfor automatically disabling the supply of power to said transducer upona termination of motion of said probe in said preselected direction,wherein said handpiece includes a main body portion and a handgripmovably attached to said main body portion, said probe being stationaryor fixed with respect to said main body portion of said handpiece, andsaid switching device including electrical contacts mounted to said mainbody portion and said handgrip, said electrical contacts beingoperatively connected to said circuit and said transducer for enablingthe supply of power to said transducer during a motion of said probe ina preselected direction defined relative to said handpiece and forautomatically disabling the supply of power to said transducer upon atermination of motion of said probe in said preselected direction.